[OpenAFS] fine-grained incrementals?

[Mike Fedyk]

Jeffrey Hutzelman wrote:

> AFS does copy-on-write at the per-vnode layer.  Each vnode has 
> metadata which is kept in the volume's vnode indices; among other 
> things, this includes the identifier of the physical file which 
> contains the vnode's contents (for the inode fileserver, this is an 
> inode number; for namei it's a 64-bit "virtual inode number" which can 
> be used to derive the filename). The underlying inode has a link count 
> (in the filesystem for inode; in the link table for namei) which 
> reflects how many vnodes have references to that inode.  When you 
> write to a vnode whose underlying inode has more than one reference, 
> the fileserver allocates a new one for the vnode you're writing to, 
> and copies the contents.

OK, I get it now.  An inode fileserver uses the link count on the 
underlying filesystem (ext3 for instance), and a namei server uses a 
large file (or possibly block device) with an AFS specific filesystem 
format.  Is that right?

I was under the impression that all AFS fileservers used the large file 
or block device (namei) system.